Enhanced Charge Carrier Transport and Device Performance Through Dual-Cesium Doping in Mixed-Cation Perovskite Solar Cells with Near Unity Free Carrier Ratios

Abstract

PbI-enriched mixed perovskite film [FAMAPb(IBr)] has been widely studied due to its great potential in perovskite solar cell (PSC) applications. Herein, a FAMAPb(IBr) film has been fabricated with the temperature-dependent optical absorption spectra utilized to determine its exciton binding energy. A ∼13 meV exciton binding energy is estimated, and a near-unity fraction of free carriers out of the total photoexcitons has been obtained in the solar cell operating regime at equilibrium state. PSCs are fabricated with this mixed perovskite film, but a significant electron transport barrier at the TiO-perovskite interface limited their performance. CsCO and CsI are then utilized as functional enhancers with which to substantially balance the electron and hole transport and increase the carriers (both electrons and holes) mobilities in PSCs, resulting in much-improved solar-cell performance. The modified PSCs exhibit reproducible power conversion efficiency (PCE) values with little hysteresis effect in the J-V curves, achieving PCEs up to 19.5% for the CsCO-modified PSC and 20.6% when subsequently further doped with CsI.

Performance Enhancement of Tri‐Cation and Dual‐Anion Mixed Perovskite Solar Cells by Au@SiO2 Nanoparticles

“…When an external electric field (voltage) is applied across the device, one of the charge carriers can be removed at an electrode and another type cof harge carrier may drift across the photoactive layer and finally reach the opposite electrode. Then, the oscilloscope can collect the drift mobility of the charge carrier in the travelling process . Furthermore, the charge carriers mobilities within the system can be easily calculated using the heterojunction thickness, applied back voltage, and free charge transit time.…”

Formamidinium‐Based Lead Halide Perovskites: Structure, Properties, and Fabrication Methodologies

“…For example, cesium acetate incorporation during the preparation of ZnO results in improved electron injection and improved device performance . CsCO 3 treatment of the TiO 2 electron‐transport layer, combined with CsI doping of perovskite, has resulted in the high‐performance perovskite devices . Performance improvement has also been reported for CsBr‐modified TiO 2 …”

Caesium for Perovskite Solar Cells: An Overview

“…As an alternative, Ye et al utilized Cs 2 CO 3 and CsI as functional enhancers,s ubstantially balancing the electrons and holes transport and increasing the mobility of the carriers. [207] The modified PSCs exhibited reproducible PCE values with little hysteresis in the J-V curves, achieving efficiencies up to 19.5 and 20.6 %f or the Cs 2 CO 3modified and CsI-doped cells, respectively.T he dream for PSCs remains that of approaching as table and reproducible technology because it has also been important for DSSCs [208][209][210][211][212][213][214][215][216][217][218][219][220][221] and other energy-relatedd evices. [222][223][224][225][226][227][228][229][230][231] Caesium-Doped Perovskites in Emerging Technologies Enhanced optical absorption, long carrierd iffusion length and high carrierm obility of perovskite materials can also be exploitedi no ther applications than standard solar cells.…”

“…As an alternative, Ye et al. utilized Cs 2 CO 3 and CsI as functional enhancers, substantially balancing the electrons and holes transport and increasing the mobility of the carriers . The modified PSCs exhibited reproducible PCE values with little hysteresis in the J‐V curves, achieving efficiencies up to 19.5 and 20.6 % for the Cs 2 CO 3 ‐modified and CsI‐doped cells, respectively.…”