Light Processing Enables Efficient Carbon-Based, All-Inorganic Planar CsPbIBr₂ Solar Cells with High Photovoltages

Abstract

Inorganic halide perovskite CsPbIBr2 possesses the most balanced band gap and stability characters among all of the concerned analogs for carbon-based, all-inorganic solar cells that are free of any hole-transporting layers and noble-metal electrodes. Yet, the current CsPbIBr2 solar cells seem to deliver the lowest record efficiency. This is originally plagued by a serious energy loss (E loss) in the cells, which thus limits their open-circuit voltages (V oc) severely. Herein, we demonstrate a light-processing technology that can overcome this obstacle successfully, by enabling the full-coverage, pure-phase CsPbIBr2 films featured with large grains, high crystallinity, and preferential [100] grains orientation, along with favorable electronic structure. It is achieved by the exposure of CsPbIBr2 precursor film formed in a conventional one-step spin-coating route to a simulated AM 1.5 G illumination before thermal annealing. The resulting carbon-based, all-inorganic planar cells give an optimized power conversion efficiency (PCE) of 8.60% with the V oc of 1.283 V. Notably, such an impressive V oc stands the highest value among all of the previously reported CsPbIBr2 solar cells; hence, its PCE exceeds nearly all of them. Therefore, our work suggests a new route to further improve the efficiency of low-cost, stable, and simple-fabrication CsPbIBr2 solar cells.

Inorganic CsPbIBr2‐Based Perovskite Solar Cells: Fabrication Technique Modification and Efficiency Improvement

“…After spin coating, a high‐temperature annealing process is often performed to remove organic components and crystalize the films. However, as shown in Figure a 2 , b 2 , and c 2 , the fabricated films usually exhibit a low surface coverage with massive micrometer‐sized voids, which would generate a risk on shutting paths for device deterioration . The formation of pinholes is believed to be resulted from the extremely slow crystallization of CsPbIBr 2 grains, where plenty of DMSO molecules are contained during crystallization and then shrink to leave isolated voids behind.…”

“…Thereinto, it has been certified that the spin‐coating process is the most convenient way for perovskite films. However, according to a series of reports, we find that the deposition of the high‐quality CsPbIBr 2 film is still very challenging, because there are apparent pinholes and massive grain boundaries on the surface . Expressly, the voids would generate a risk on shutting paths, while the grain boundaries may form shallow states near the band edge to hinder carrier diffusion.…”

“…Both factors seriously reduce the device's photoelectric properties, thereby bringing a significant obstacle to the further application of the spin‐coating method. Hence, many assisting procedures have been attempted to overcome this dilemma . Intermolecular exchange, as a representative, was integrated with the spin‐coating method to achieve the preparation of the full‐coverage and top‐quality CsPbIBr 2 films .…”

“…The crystal structure of the CsPbIBr 2 material was concisely introduced as a beginning, followed by the various fabrication procedures of perovskite films. Subsequently, some novel strategies were presented for film quality improvement, including fabrication methods’ improving, interface engineering, element impurity doping, etc . As a consequence, optoelectronic properties of the perovskite films by these methods are drastically improved.…”

Anorganische CsPbX3‐Perowskit‐Solarzellen: Fortschritte und Perspektiven

“…[143,144] Allerdings wurde gezeigt, dass CsPb(Br x I 1Àx ) 3 (fürx> 0.4) unter Lichteinfall einer Phasentrennung in I-und Br-reiche Phasen unterliegt. [143,144] Allerdings wurde gezeigt, dass CsPb(Br x I 1Àx ) 3 (fürx> 0.4) unter Lichteinfall einer Phasentrennung in I-und Br-reiche Phasen unterliegt.…”