Enhancing Efficiency and Stability of Perovskite Solar Cells through Nb-Doping of TiO₂ at Low Temperature

Abstract

The conduction band energy, conductivity, mobility, and electronic trap states of electron transport layer (ETL) are very important to the efficiency and stability of a planar perovskite solar cell (PSC). However, as the most widely used ETL, TiO often needs to be prepared under high temperature and has unfavorable electrical properties such as low conductivity and high electronic trap states. Modifications such as elemental doping are effective methods for improving the electrical properties of TiO and the performance of PSCs. In this study, Nb-doped TiO films are prepared by a facile one-port chemical bath process at low temperature (70 °C) and applied as a high quality ETL for planar PSCs. Compared with pure TiO, the Nb-doped TiO is more efficient for photogenerated electron injection and extraction, showing higher conductivity, higher mobility, and lower trap-state density. A PSC with 1% Nb-doped TiO yielded a power conversion efficiency of more than 19%, with about 90% of its initial efficiency remaining after storing for 1200 h in air or annealing at 80 °C for 20 h in a glovebox.

Review of Recent Progress in Antimony Chalcogenide‐Based Solar Cells: Materials and Devices

“…The ZnO NW structure enhanced the optical absorption by the light‐trapping effect of the NWs and reduced the bulk recombination rate in the Sb 2 S 3 from the shortened electron injection pathway, resulting in a PCE of 2.9% with a high J SC of ≈16 mA cm −2 . Regarding the conventional TiO 2 ETL, various methods such as doping TiO 2 ETL with Nb and treating TiO 2 with Mg or Ba anions have been used to improve the electron transport efficacy . Very recently, an ultrathin SiO 2 blocking layer was incorporated in Sb 2 S 3 ‐sensitized solar cells to suppress interfacial recombination, resulting in a better device performance of 3.96% …”

Tailoring electrical property of the low-temperature processed SnO2 for high-performance perovskite solar cells

“…As illustrated in Fig. S7 and Table S4, the hysteresis ratio, defined as (PCE reverse -PCE forward )/PCE reverse , was decreased by doping 0.5% and 1% Nb in SnO 2 , which was probably attributed to the accelerated charge injection and transport in the ETL, resulting in the decreased charge accumulation at perovskite/SnO 2 interface [36,41]. The photo-stability of PSCs was also studied under ultraviolet light with intensity of 80 mW cm −2 (Fig.…”

“…The significant increase of conductivity could accelerate the charge transport in the SnO 2 ETL and reduce the probability of non-radiative recombination [36,41]. Subsequently, the bandgap of SnO 2 with and without Nb 5+ doping was measured by UV-vis spectra.…”

Stability Challenges for Perovskite Solar Cells

“…Yin et al. reported a low‐temperature and solution‐processed chemical bath method to dope Nb into TiO 2 films for a high electrical conductivity, high electron mobility and low trap‐state density TiO 2 ETL . PCE can maintain at around 90% of its initial efficiency after storing in air for 1,200 h.…”