A novel approach for designing efficient broadband photodetectors expanding from deep ultraviolet to near infrared

Broadband photodetection (PD) covering the deep ultraviolet to near-infrared (200–1000 nm) range is significant and desirable for various optoelectronic designs. Herein, we employ ultraviolet (UV) luminescent concentrators (LC), iodine-based perovskite quantum dots (PQDs), and organic bulk heterojunction (BHJ) as the UV, visible, and near-infrared (NIR) photosensitive layers, respectively, to construct a broadband heterojunction PD. Firstly, experimental and theoretical results reveal that optoelectronic properties and stability of CsPbI3 PQDs are significantly improved through Er3+ doping, owing to the reduced defect density, improved charge mobility, increased formation energy, tolerance factor, etc. The narrow bandgap of CsPbI3:Er3+ PQDs serves as a visible photosensitive layer of PD. Secondly, considering the matchable energy bandgap, the BHJ (BTP-4Cl: PBDB-TF) is selected as to NIR absorption layer to fabricate the hybrid structure with CsPbI3:Er3+ PQDs. Thirdly, UV LC converts the UV light (200–400 nm) to visible light (400–700 nm), which is further absorbed by CsPbI3:Er3+ PQDs. In contrast with other perovskites PDs and commercial Si PDs, our PD presents a relatively wide response range and high detectivity especially in UV and NIR regions (two orders of magnitude increase that of commercial Si PDs). Furthermore, the PD also demonstrates significantly enhanced air- and UV- stability, and the photocurrent of the device maintains 81.5% of the original one after 5000 cycles. This work highlights a new attempt for designing broadband PDs, which has application potential in optoelectronic devices.


Introduction
Photodetectors (PDs) are the technical functional components for capturing and converting ultraviolet (UV) to near-infrared (NIR) photons into electronic outputs [1][2][3][4][5] . The broadband optical detection ability, especially from UV to NIR range, is critical for applications including medical monitoring, video imaging, optical communication, and civil engineering [6][7][8][9][10][11][12] . Generally, the commercial silicon PDs present the relatively broad wavelength response range from 400-1100 nm 13,14 , but usually suffer from high cost and low detectivity, especially in the UV region. Solution-processable broadband PDs based on soluble materials have numerous advantages of low cost, simple preparation, and high sensitivity, which has become the next generation of new detectors [15][16][17] .
Encouragingly, solution-processable metal halide perovskites process outstanding characteristics of large absorption coefficient, long diffusion length, low trapping density, and high photoluminescent quantum efficiency (PLQY), which have shown unprecedented radical progress for various optoelectronic devices, including solar cells (SCs), light-emitting diodes (LEDs), and photodetectors (PDs) 11,18,19 . Among them, all-inorganic perovskite quantum dots (ABX 3 , A = Cs; B = Pb, Ge, Sn; X = Cl, Br, I) (PQDs) have attracted extensive interest in broadband PDs, owing to their wide-range tunability of bandgap, large absorption cross-section, high carrier mobility, etc 18,[20][21][22][23] . Especially, CsPbI 3 PQDs process narrow bandgap of 1.73 eV, becoming a candidate for broadband PDs 24 . For example, Tian et al. fabricated 2-aminoethanethiol (AET)/CsPbI 3 PQDs compositebased PDs device, exhibiting a high responsivity of 105 mA W −1 and the detection wavelength covering the visible light 22 . However, its spectrum covers mainly the blue to visible light range (400-700 nm), short of UV response and NIR absorption, due to the insensitivity to UV light and limitation of the bandgap. In addition, they also encounter relatively high trap density, poor carrier mobility, and high susceptibility to moisture and UV light, generating phase transition from cubic to orthorhombic phase [25][26][27] . The above issues severely limit its photodetection of broadband response spectrum with high stability and responsivity.
To overcome the challenges mentioned above, much efforts have been made to improve the stability and responsivity, and to expand the spectral response range of perovskite-based PDs. A number of metal ions (eg., Zn 2+ , Cr 3+ , Nd 3+ , Er 3+ , Ce 3+ ) doping have been proved to be a promising way to boost the optical and electrical performance of perovskite materials [28][29][30][31] , including the decrease of trap density and the improvements of carrier mobility, stability, and photoluminescence quantum yield (PLQY). Meanwhile, the strategy of integrating perovskite with NIR absorption materials (e.g., organic bulk heterojunction (BHJ), lead sulfide quantum dots, etc.) was attempted to expand the spectral response range of PDs to the NIR region [32][33][34] . For example, Chen et al. achieved broadband photodetectors with high NIR external quantum efficiency of over 70% in organic-inorganic perovskite/BHJ hybrid 35 . Nevertheless, such PD has low responsivity in the UV region and relatively poor stability of organic-inorganic perovskite.
The scheme of luminescent conversion was proven to be an effective route to enlarge the response to the UV by absorbing and converting UV to visible photons and further being captured by PD. The luminescent conversion films consisting of Cr 3+ , Ce 3+ , Yb 3+ tridoped CsPbCl 3 PQDs or carbon dots were explored to boost the UV response of silicon PDs [36][37][38] . As a class of excellent luminescent conversion materials, luminescent concentrator (LC) consists of transparent polymer sheets doped with luminescent species that can be employed as a nonimaging optical device that collects and concentrates light energy 39,40 . It has been widely applied in photovoltaic cells or optical communications to largely improve the power conversion efficiency 41,42 .
In this work, we represent the design and fabrication of a novel type of hybrid PDs based on ultraviolet (UV) luminescent concentrators (LC) and doped PQDs and an organic bulk heterojunction, which can realize efficient photodetection in the whole range of 200-1000 nm. The device integrates a tridoped PQDs (CsPbCl 3 :Cr 3+ ,Ce 3+ , Mn 2+ ) photoluminescent layer to harvest and converts UV light to visible, a CsPbI 3 :Er 3+ layer to realize the photoelectric conversion of visible light, and an organic bulk heterojunction to extend photoelectric response to NIR light. In such a device, CsPI 3 :Er 3+ PQDs was explored as the visible photoelectric layer. Doping of Er 3+ largely improved the radiative transition rate of the perovskite excitons and structure stability, altered charge carrier transport of CsPbI 3 QDs, thus leading to performance enhancement considerably. In CsPbCl 3 :Cr 3+ ,Ce 3+ , Mn 2+ based LC, Mn 2+ ions convert the UV to red lights, locating within the optimum regions of CsPbI 3 :Er 3+ based PD, and simultaneously, Cr 3+ and Ce 3+ doping significantly improve PLQY of the PQDs and enhance lightharvesting of UV light for PQDs due to the coupling of 5d states of Ce 3+ with the PQDs, extremely in the deep UV (DUV) region. In addition, an organic BHJ (BTP-4Cl: PBDB-TF) with an absorption extending 1000 nm was adopted as NIR photoelectric layer to integrate with CsPbI 3 :Er 3+ layer. Taking all advantages above, the present PDs realize the spectral response spanning from 200 to 1000 nm and demonstrated detectivity reaching 10 12 Jones. Figure 1a and S1 illustrates the structure and the crosssectional scanning electron microscopy (SEM) images of the broadband PDs, which consists of CsPbCl 3 :Cr 3+ ,Ce 3+ , Mn 2+ PQDs doped polymethyl methacrylate LC (Cr/Ce/ Mn-LC)/ITO/SnO 2 :Ti 3 C 2 /CsPbI 3 :Er 3+ PQDs/PBDB-TF: BTP-4Cl (BHJ)/Ag. Firstly, the SnO 2 :Ti 3 C 2 ETL (~50 nm) was spin-coated on ITO substrate and then annealed at 150°C for 15 min. The CsPbI 3 :Er 3+ PQDs with a thickness of 450 nm were fabricated on the ETL modified ITO glass by spin-coating. Then the organic BHJ of PBDB-TF: BTP-4Cl as an NIR photosensitive layer was deposited on top of the CsPbI 3 :Er 3+ PQDs film. Finally, the Cr/Ce/Mn-LC was positioned at the ITO side to construct the UV-Visible-NIR PD. The mixture of BHJ can absorb the low-energy NIR photons and effectively passivate the defects in the perovskite film and improve carrier transport and collection (Fig. 1b) 43 . As demonstrated in Fig. 1c, CsPbI 3 :Er 3+ PQDs has good absorption in the range of 350-700 nm, BHJ exhibits light absorption in the range of 700-1000 nm, and the CsPbI 3 :Er 3+ PQDs/BHJ film shows the absorption band from 350 to 1000 nm. Differently, the detected lights with a wavelength within 200-400 nm, are completely absorbed by Cr/Ce/Mn-LC and converted to 400-700 nm, which are further absorbed by CsPbI 3 :Er 3+ PQDs. Finally, combining UV-Visible-NIR absorption of Cr/Ce/Mn-LC and CsPbI 3 :Er 3+ PQDs and BHJ, the fabricated PDs can exhibit a wide photodetection range from 200 to 1000 nm.
The Er 3+ doping concentration dependence of PL lifetimes (τ) and transition rates of CsPbI 3 and CsPbI 3 :Er 3+ PQDs were measured ( Fig. 2e and S9). It can be observed that the PL lifetimes gradually decrease from 168 ns of CsPbI 3 PQDs to 69 ns of CsPbI 3 :Er 3+ (9.7%) PQDs. The radiative rates (k r ) and nonradiative rates (k nr ) of CsPbI 3 and CsPbI 3 :Er 3+ PQDs were calculated in Table S2 according to the following equations: k r = PLQY/τ, and k nr = (1-PLQY)/τ. Compared to the CsPbI 3 PQDs, the k r of CsPbI 3 :Er 3+ (7.7%) PQDs increases about 3.6-folds and the k nr of CsPbI 3 :Er 3+ (7.7%) PQDs decreases about 3.5folds. It suggests that the Er 3+ doping can boost the radiative decay rate, reduce the trap density and enhance the PLQY of PQDs. The increase of the radiative decay rate in CsPbI 3 :Er 3+ (7.7%) PQDs can be proved by the decreased power index as a function of the excitation power density (Fig. S10) 51 .
The role of Er 3+ in the electrical conductivity of PQDs films were studied using I-V curves of the ITO/PQDs  . A larger built-in potential value means an enhanced driving force for the separation of photogenerated carriers as well as an extended depletion region for efficient suppression of electron-hole recombination, which is favorable for carrier separation, transport, and extraction [52][53][54] . The built-in potential (V b ) values of CsPbI 3 :Er 3+ PQDs is larger than that of CsPbI 3 PQDs, realizing the more effective separation of photogenerated carriers after Er 3+ doping. It should be highlighted that incorporating Er 3+ ions into CsPbI 3 PQDs demonstrates significantly enhanced air-and UV-stability, which is of great importance for practical applications 35,55,56 . The PL intensity of CsPbI 3 : Er 3+ (7.7%) PQDs still maintains above 97 and 67% of its initial value after 30 days of storage and 10 h UV light radiation, but the PL of CsPbI 3 PQDs almost disappears after 5 days storage and 8 h UV light radiation ( Fig. 2h and Figs. S11, S12). The thermal stability of CsPbI 3 PQDs is also improved remarkably after Er 3+ doping, which PL intensity remains 87% after annealing at 390 K, and no PL is recorded for CsPbI 3 PQDs after annealing at 350 K. Considering the better conductivity, the CsPbI 3 and CsPbI 3 :Er 3+ (7.7%) PQDs are further treated with ethyl acetate to remove the original long-chain ligands of oleic acid (OA) and oleylamine (OAm) of PQDs 57,58 . The CsPbI 3 :Er 3+ PQDs demonstrate outstanding air-and UVstability (Fig. S13).
We next performed density functional theory (DFT) calculations aimed at understanding the origin of Er 3+ doping-induced changes in structural and photophysical properties of CsPbI 3 PQDs. Electronic structures and formation energy of intrinsic vacancies with different charge states (q i ) at Pb rich and I poor condition in pure cubic CsPbI 3 and Er 3+ doped CsPbI 3 were calculated using Perdew-Burke-Ernzerhof (PBEsol) functional without considering the spin-orbit coupling effect (Supplementary Note 5) 59 . Fig. 3a illustrate the electronic structure and density of states (DOS) of pure cubic CsPbI 3 (2 × 2 × 2 supercell, 8fu/cell) with direct bandgap 1.72 eV and internal symmetry breaking. The I 5p and Pb 6 s orbital mainly contribute to the valance band maximum (VBM), and Pb 6p and I 5p dominate the conduction bands minimum (CBM). As shown in Fig. 3b, the bandgap of CsPbI 3 :Er 3+ is larger than pristine CsPbI 3 , and the band edge states of CsPbI 3 :Er 3+ (8 fu/cell) does change (i.e., VBM and CBM), presenting the bandgap increase to 1.82 eV. We also theoretically calculated the formation energy of intrinsic vacancy defects of Cs, Pb, and I (labeled as V Cs , V Pb , and V I ) in pure cubic CsPbI 3 and CsPbI 3 :Er 3+ (64 fu/cell) by using PBEsol functional and 2 × 2 × 2 k-grid. As illustrated in Fig. 3c, d and Tables S3, S4, the intrinsic vacancies in CsPbI 3 are shallow defects with relatively smaller formation energy, which shows larger formation energy in CsPbI 3 :Er 3+ , leading to the reduced trap density after Er 3+ doping, similar to the experimental results in Fig. 2d. Generally, the defects can act as carrier traps, resulting in nonradiative recombination, whereas fewer defects largely preserve the bulk electronic band structure and can improve the optoelectronic properties of PQDs 31,60 . Table 1 lists the formation energy of ternary compounds to the corresponding binary compounds by DFT. The calculated formation energy ΔH f of CsPbI 3 :Er 3+ reveals that the reaction spontaneously occurs starting from binary precursors because of the exothermic reaction. The reaction path is: CsI + Er 3+ I 2 + e + PbI 2 -> Cs 8 Pb 7 ErI 24 + e. The calculated formation energy ΔH f (defined in Table 1) of Er 3+ doped CsPbI 3 with respect to binary precursors CsI, Er 3+ I 2 , and PbI 2 is positive, referring to the exothermic reaction 61 . This indicates that the reaction CsI + 0.077(ErI 3 ) + 0.923(PbI 2 ) ->CsPb 0.923 Er 0.077 I 3 spontaneously can occur. The formation energy of CsPbI 3 : Er 3+ PQDs is larger than prsitine CsPbI 3 PQDs, which demonstrate the CsPbI 3 :Er 3+ PQDs are more energetically stable than CsPbI 3 PQDs. Moreover, the chemical potential in 2 × 2 × 2 supercell of cubic CsPbI 3 was calculated by considering the binary competing phase CsI and PbI 2 . As illustrated in Fig. 3e, f, the chemically stable range for cubic CsPbI 3 is smaller than CsErI 3 . Meanwhile, the formation energy and tolerance factors of CsPbI 3 become larger after Er 3+ doping (Table S1 and Fig. S14), implying the more energetically stable structure of CsPbI 3 :Er 3+ (Fig. 2h). Experimentally, the reduced defect density, the enhanced carrier densities and the conductivity, and the increased built-in potential (V b ) values of CsPbI 3 PQDs after Er 3+ doping were observed. Therefore, experimental and theoretical results demonstrate that the Er 3+ doping can reduce trap density, improve the density and mobility of carriers, accelerate carriers' separation, and enhance the stability of CsPbI 3 PQDs.
To obtain Cr/Ce/Mn-LC, the homogeneous and cubic Cr 3+ , Cr 3+ /Mn 2+ , and Cr 3+ /Mn 2+ /Ce 3+ doped CsPbCl 3 PQDs were successfully prepared by the modified hotinjection method 37,65 as revealed in TEM images, XRD patterns, and XPS spectra in Figs. S17-19. Figure 4e shows the UV-Vis absorption spectra of pristine and  (Fig. S20). Surprisingly, the PLQY of CsPbCl 3 :Cr 3+ , Mn 2+ , Ce 3+ PQDs is measured to be 93.5%. According to the previous literatures 68, 69 , such high PLQY (Fig. 4f) are mainly due to the reduced nonradiative decay rate after Cr 3+ doping, the boosted energy transfer from PQDs to Mn 2+ ions and the enhanced UV absorption after Ce 3+ doping. The energy transfer mechanism of CsPbCl 3 :Cr 3+ , Mn 2+ , Ce 3+ PQDs is presented in Fig. 4g. Importantly, the doping with Cr 3+ , Mn 2+ ,Ce 3+ can also largely improves the stability of CsPbCl 3 PQDs, in which the PL intensity remains around 93% after 30 days (Fig. S21). In virtue of high conversion efficiency from UV to visible lights, the CsPbCl 3 :Cr 3+ , Mn 2+ , Ce 3+ PQDs are embedded into a PMMA polymer matrix to form a Cr/Ce/Mn-LC (inset of Fig. 4h). The Cr/ Ce/Mn-LC demonstrates the similar emission spectra with CsPbCl 3 :Cr 3+ ,Mn 2+ ,Ce 3+ PQDs ( Fig. 4h and S22) and high transparency to visible lights (Fig. S23). The face emission of the PLQY Cr/Ce/Mn-LC is 20.03%, which is lower than the edge emissions (61.47%) due to the total internal reflection to the edges in the LC (Fig. S24). Such Cr/Ce/Mn-LC processes the high efficiency and transparency, can be severed as a photoluminescent converter to boost the UV response of PD. Figure 5a shows the charge generation and transport mechanism of the broadband PDs with the response range spanning from UV to NIR lights, in which PQDs straightly absorb the visible lights, the BHJ layer captures the NIR lights, Cr/Ce/Mn-LC converts the UV lights (200-400 nm) to visible lights (400-700 nm) further absorbing by PQDs. The photocurrent-time (I-t) response curves based on the ITO/ETL/CsPbI 3 PQDs/Ag (S1), ITO/ETL/CsPbI 3 :Er 3+ (7.7%) PQDs/Ag (S2), ITO/  PQDs resulting in increased carriers mobility, and accelerated carriers transport (Fig. 2). BHJ hybridization not only significantly boosts the photocurrent of 860 nm owing to the direct NIR absorption, but also contributes to the slight increase of photocurrent at 460 nm (S3) due to the inhibited electron-hole pair recombination at the interfaces of CsPbI 3 :Er 3+ (7.7%) PQDs/BHJ film. It can be seen that the photocurrent of Cr/Ce/Mn-LC surface is 0.092 mA, which increases to 0.32 mA for the side edge of S4 PDs. The improvement of photocurrent at 260 nm mainly originates from the waveguide structure and the highly improved light collecting efficiency 70 . Moreover, the photocurrent response of PDs using PMMA: CsPbCl 3 : Cr 3+ , Mn 2+ , Ce 3+ luminescent conversion layer (0.105 mA) is also lower than that of Cr/Ce/ Mn-LC (0.32 mA). In the luminescent conversion layer, the direction of visible emissions are random under UV illumination, and only the emission photons which irradiate on the PD can be utilized. But in the Cr/Ce/Mn-LC, most of the emission photons can be traveled to the edge side attached to PD. Thus, the improvement of photocurrent in Cr/Ce/Mn-LC mainly originates from the waveguide structure and the highly improved light (400-700 nm) concentrate efficiency. The dark currents of the S2-S4 PDs are lower than that of the pristine PD device by one to two orders of magnitude, suggesting the defect sites of PQDs are effectively passivized by Er 3+ doping and BHJ hybridization (Fig. S27), consistently with the results in Figs. 2, 4a-d 46,71 . In line with the decreased dark current of S3 and S4 PDs, the θ coefficients in the S3 and S4 PDs (θ = 0.763 and 0.767) have better linearity than the pristine PD (θ = 0.698), following  Fig. 5 Performance of broadband PDs. a Charge generation and transport mechanism of a broadband PD. b Photocurrents of the ITO/ETL/CsPbI 3 / Ag (S1), ITO/ETL/CsPbI 3 :Er 3+ (7.7%) PQDs/Ag (S2), ITO/ETL/CsPbI 3 :Er 3+ (7.7%) PQDs/BHJ/Ag (S3) and Cr/Ce/Mn-LC/ITO/ETL/CsPbI 3 :Er 3+ (7.7%) PQDs/ BHJ/Ag (S4) devices under the 260 nm, 460 nm, and 860 nm, respectively. c D* of the S1-S4 devices and commercial Silicon PD. d EQE of the S1-S4 devices. e, f Stability of the S1-S4 devices under 30% RH and UV light radiation the power-law I ∼ P θ , where I and P represent the photocurrent and the incident light power intensity (Fig. S28) 72 . Figs. 5c, d and S29 display the detectivity (D*), external quantum efficiency (EQE), and photoresponsivity (R) of S1-S4 PDs. These three parameters satisfy the following equations 20,37 : where I ph and I d are the photocurrents under the illumination of light and in the dark, P and S are the input light power density and the effective irradiated area, h and c are the Planck's constant and the speed of light, λ and e are the incident light wavelength and the elementary charge. The pristine S1 PD presents the low D*, EQE, and R in the whole region. Those values are largely boosted in the visible region in S2-S4 PDs, and simultaneously, its responses expand to NIR (S3 PD) and UV (S3 and S4 PD) regions.  (Fig. S30). The longterm stability of the S1-S4 PDs was further studied. As displayed in Fig. 5e, the S2-S4 PDs maintain about 82% of the initial photocurrent, while the photocurrent of the S1 device dropped to 0% after 60 h, owing to the outstanding stability of PQDs by Er 3+ doping. The UV stability of the S1-S4 devices in Fig. 5f illustrates that the stability of S2-S4 PDs are large improved, especially, S4 PD represents the best UV light stability, maintaining above 86% of the initial photocurrent after 10 h UV illumination, but it degrades to 0% for pristine PD within 7 h. The reason for those improvements in the air-and UV-stability are mainly attributed to the role of Er 3+ doping, BHJ hybridization, and the buffer layer of Cr/Ce/ Mn-LC in the device. Notably, the photocurrent of the PD is repeatable even after five thousand cycles (Fig. S31), confirming the excellent reversibility of this photodetector. Compared to the previous broadband perovskite PDs (Table 2), our device exhibits excellent performance with a relatively wide response, high responsivity, and detectivity, especially in UV and NIR regions, and good stability, which exceeds the results of the previous reports.

Discussion
In this work, unique broadband PDs with the response range of 200-1000 nm and the D* value reaching of 1.14 × 10 12 at 260 nm and 2.46 × 10 12 at 460 nm, and 1.85 × 10 12 at 860 nm based on doped PQDs and an organic bulk heterojunction and Cr/Ce/Mn-LC were reported. Several new contributions for developing broadband PDs in this work should be highlighted. Firstly, CsPbI 3 :Er 3+ PQDs serve as a visible photosensitive layer of PD, and the performance improves two orders that of

Synthesis of Cs-oleate
About 0.8 g Cs 2 CO 3 was added into a mixture of 30 mL of ODE and OA (2.5 mL) and then heated to 150°C and the white powder was completely dissolved. The mixture was then kept at 120°C.

Synthesis of CsPbI 3 PQDs
PbI 2 (0.3 mmol), OAm (1.5 mL), OA (1.5 mL), and ODE (10 mL) were added to a 50-mL three-neck roundbottomed flask and were evacuated and refilled with N 2 , followed by heating the solution to 120°C for 1 h. The temperature of the solution was then increased to 180°C for 10 min. Then, the Cs-oleate (1 mL) was swiftly injected into the solution. After 10 s, the solution was cooled in an ice bath. The CsPbI 3 PQDs were precipitated and then centrifuged, followed by dissolution in toluene.

Synthesis of Er 3+ doped CsPbI 3 PQDs
PbI 2 (0.3 mmol) and ErI 3 (0.15 mmol) were loaded into round-bottom flask with OAm (1.5 mL), OA (1.5 mL), and ODE (10 mL). It was continued heated at 120°C for 2 h and refilled with N2. Then the solution was increased to 230°C. Then, the Cs-oleate (1 mL) was swiftly injected into the solution. After 10 s, the solution was cooled in an ice bath. Finally, the CsPbI 3 :Er 3+ (7.7 %) PQDs were precipitated and then centrifuged, followed by dissolution in toluene.
Fabrication of Cr/ Ce /Mn -LC About 0.8 g PMMA (MW~350000) was dispersed in 5 mL toluene by sonication, to which 2.5 mL toluene solution of CsPbCl 3 : Cr 3+ (8.3%),Ce 3+ (3.2%),Mn 2+ (9.3%) PQDs were added. The mixture was sealed and stirred overnight to obtain a homogenous slurry. The slurry was centrifuged at 2000 rpm and the supernatants were used for LC fabrication. The above supernatants were dropped onto borosilicate glass substrates and LC was fabricated by spin-coating.

Syntheses of BHJ film
The PBDB-TF:BTP-4Cl (1:1.2) was dissolved in chloroform. The mixture was heated and stirred at 60°C for 5 h to obtain an organic active layer solution. The solvent additive of 1-chloronaphthalene (CN) (0.5%) was added half an hour before the organic active layer solution deposition. For the hybrid PDs, the PBDB-TF:BTP-4Cl solution was spincoated on a perovskite layer at 1800 rpm for 60 s and subsequently annealed at 80°C for 10 min.

Device fabrication
ITO-coated glass substrates were etched with zinc powder and HCl to define the electrode patterns and washed in deionized water, acetone, and ethanol for 20 min, respectively. The ultraviolet ozone was used to remove the organic residues of the ITO surface. To fabricate the compact SnO 2 :Ti 3 C 2 layer, the SnO 2 :Ti 3 C 2 colloid solution by water to the concentration of 2.14 wt% was spin-coated on ITO substrates at 5000 rpm for 30 s and then annealed at 150°C for 30 min. The Er 3+ doped CsPbI 3 PQDs film was fabricated on the SnO 2 :Ti 3 C 2 layer by spin-coating at 600 rpm for 6 s and 4000 rpm for 40 s, respectively. The PBDB-TF in chlorobenzene (CB) (400 μL) at various concentrations was dropped on a substrate at 20 s before the end of the spinning process. After that, the PBDB-TF:BTP-4Cl solution was spincoated on a perovskite layer at 1800 rpm for 60 s and subsequently annealed at 80°C for 10 min. The Ag electrode was deposited by thermal evaporation to complete the device fabrication. Then, the edge surface of Cr/Ce/ Mn-LC with an edge size of 0.1 × 0.04 cm was attached and fixed to the ITO layer of PD with an area of 0.1 × 0.1 cm. When UV light radiation on the face of Cr/Ce/ Mn-LC, then the emitted 400-700 nm light is coupled out of the edge surface into the ITO of PDs. The visible and NIR lights directly pass through the ITO and reach the PD. Because the Cr/Ce/Mn-LC only occupies a part of the surface of the ITO layer and has high transparency for photons with a longer wavelength (>410 nm), which would not affect the light collection of PD.
Characterization UV/vis-NIR absorption spectra were measured with a Shimadzu UV-3600PC UV/vis-NIR scanning spectrophotometer in the range from 200 to 2500 nm. Patterns were recorded in thin-film mode on a Bruker AXS D8 diffractometer using Cu Kαradiation(λ = 1.54178 Å). Atomic Force Microscope (AFM) was performed using a DI Innova AFM (Bruker) in light tapping mode. The morphology of the products was recorded with a Hitachi H-8100IV transmission electron microscope (TEM) under an acceleration voltage of 200 kV. The samples were pumped using a laser system consisting of a tunable optical parameter oscillator (OPO, Continuum Precision II 8000) with a pulse duration of 10 ns, a repetition frequency of 10 Hz, and a line width of 4-7 cm −1 . A visible photomultiplier (350-850 nm) combined with a doublegrating monochromator were used for spectral collection. The X-ray photoelectron spectroscopy (XPS) was carried out in a Kratos Axis Ultra DLD spectrometer equipped with a monochromatic Al Kα X-ray source (hν = 1486.6 eV) operated at 150 W with a multichannel plate, and a delay line detector under 1.0 × 10 −9 Torr vacuum. A photomultiplier combined with a monochromator was used for dynamics signal collection of samples from 350 to 850 nm. Nanosecond fluorescence lifetime experiments were performed by the timecorrelated single-photon counting system (HORIBA Scientific iHR 320). Absolute photoluminescence quantum yield measurements were performed on colloidal CsPbCl 3 :Cr 3+ ,Ce 3+ ,Mn 2+ and CsPbI 3 :Er 3+ PQDs (dispersed in toluene placed in a sealed 1 cm path length quartz cuvette) and Cr/Ce/Mn-LC. They were positioned in a Teflon-based integrating sphere using a custom cuvette holder and directly excited with a 365 nm Xe lamp. The typical PLQY in such a system is estimated as follows: with the spectral range from 200 to 2500 nm equipped with a monochromator (Omni-λ3007i, Zolix) was used to generate the monochromatic light to conduct the spectral response measurements. Actually, the intensity of the Xe lamp is weak in the region of 200-300 nm, thus we must correct it before the measurement.