Simultaneous Lattice Engineering and Defect Control via Cadmium Incorporation for High‐Performance Inorganic Perovskite Solar Cells

Abstract

Doping of all-inorganic lead halide perovskites to enhance their photovoltaic performance and stability has been reported to be effective. Up to now most studies have focused on the doping of elements in to the perovskite lattice. However, most of them cannot be doped into the perovskite lattice and the roles of these dopants are still controversial. Herein,the authors introduce CdI 2 as an additive into CsPbI 3−x Br x and use it as active layer to fabricate high-performance inorganic perovskite solar cells (PSCs). Cd with a smaller radius than Pb can partially substitute Pb in the perovskite lattice by up to 2 mol%. Meanwhile, the remaining Cd stays on the surface and grain boundaries (GB) of the perovskite film in the form of Cs 2 CdI 4−x Br −x , which is found to reduce non-radiative recombination. These effects result in prolonged charge carrier lifetime, suppressed defect formation, decreased GBs, and an upward shift of energybands in the Cd-containing film. A champion efficiency of 20.8% is achieved for Cd-incorporated PSCs, together with improved device ambient stability. This work highlights the importance of simultaneous lattice engineering, defectcontrol and atomic-level characterization in achieving high-performance inorganic PSCs with well-defined structure-property relationships.

Surface Passivation of CsPbI 3 Films for Efficient and Stable Hole-Transporting Layer-Free Carbon-Based Perovskite Solar Cells

“…As can be seen, the average carrier lifetime (τ ave ) increased from 3.59 to 7.53 ns after OAI treatment, which further indicates the reduced defect density as well as nonradiative charge recombination of CsPbI 3 perovskite films after OAI treatment. 33 To quantify the defect density of CsPbI 3 films with and without OAI treatment, space-charge-limited current (SCLC) characterizations of electron-only devices were performed with a structure of FTO/compact-TiO 2 (c-TiO 2 )/mesoporous-TiO 2 (m-TiO 2 )/ CsPbI 3 /PCBM/Ag, and the corresponding SCLC plots and the calculated results are shown in Figures S8 and 3c, respectively. Clearly, the trap-filled limit voltage (V TFL ) values of CsPbI 3 perovskite films without and with OAI treatment are 0.51 and 0.44 V, respectively.…”

“…Figure b shows the TRPL spectra of CsPbI 3 films with and without OAI treatment, and the corresponding double exponential decay function fitting data are listed in Table S1. As can be seen, the average carrier lifetime (τ ave ) increased from 3.59 to 7.53 ns after OAI treatment, which further indicates the reduced defect density as well as nonradiative charge recombination of CsPbI 3 perovskite films after OAI treatment . To quantify the defect density of CsPbI 3 films with and without OAI treatment, space-charge-limited current (SCLC) characterizations of electron-only devices were performed with a structure of FTO/compact-TiO 2 (c-TiO 2 )/mesoporous-TiO 2 (m-TiO 2 )/CsPbI 3 /PCBM/Ag, and the corresponding SCLC plots and the calculated results are shown in Figures S8 and c, respectively.…”

“…24−26 Thus, HTL-free inorganic CsPbI 3 carbon-based PSCs (C-PSCs) with greatly reduced cost as well as improved long-term operation stability show promising commercial prospects. 27,28 Since the first report of HTL-free inorganic CsPbI 3 C-PSCs with a low PCE of 4.65% by Liang et al, 29 many efforts have been made to improve the efficiency of this kind of device, including composition manipulation, 30−32 element doping, 33 interface engineering, 34,35 process optimization, 13,14 etc., which significantly boost the PCE of CsPbI 3 C-PSCs to over 16% till now. 36,37 Especially, Chen's group pioneered the highefficiency CsPbI 3 C-PSCs via composition manipulation, which demonstrated that carefully controlling the precursor ratios of dimethylammonium iodide (DMAI)/PbI 2 /CsI can suppress the formation of δ-CsPbI boosting the PCE of CsPbI 3 C-PSC to 14.6%.…”

“…Since the first report of HTL-free inorganic CsPbI 3 C-PSCs with a low PCE of 4.65% by Liang et al, many efforts have been made to improve the efficiency of this kind of device, including composition manipulation, − element doping, interface engineering, , process optimization, , etc., which significantly boost the PCE of CsPbI 3 C-PSCs to over 16% till now. , Especially, Chen’s group pioneered the high-efficiency CsPbI 3 C-PSCs via composition manipulation, which demonstrated that carefully controlling the precursor ratios of dimethylammonium iodide (DMAI)/PbI 2 /CsI can suppress the formation of δ-CsPbI 3 , minimize DMAPbI 3 residual, and generate PbI 2 passivator, simultaneously, thus boosting the PCE of CsPbI 3 C-PSC to 14.6% . Later, CsCl is introduced into the surface of CsPbI 3 films to induce the formation of an energy level gradient as well as an electron blocking layer, further improving the PCE of this kind of device to 15.23% .…”

High‐Efficiency Carbon‐based CsPbI2Br Perovskite Solar Cells from Dual Direction Thermal Diffusion Treatment with Cadmium Halides

“…All the above reasons make the device after treatment have better device stability. [31,50,51] In order to explore the role of halogen ions alone, we tried to modified the surface of SnO 2 film with different concentrations of NH 4 Cl through the same method as cadmium halide. NH 4 Cl decomposes into NH 3 and HCl at 400 °C, due to the density of HCl is higher than that of air, which can adhere to the surface of the sample, resulting in a small amount of Cl − ions on the surface of SnO 2 ETL.…”