Bandtail broadening originating from increasing the polydispersity of colloidal quantum dots (CQDs) deteriorates open-circuit voltage (V OC) and hinders charge-carrier transport in CQD photovoltaics. The development of colloidal synthetic routes has enabled preparing monodisperse perovskite CQDs (Pe-CQDs) that have attracted attention as promising absorbers in CQD photovoltaics. However, polar-antisolvent-based purification induces the dissolution and agglomeration of Pe-CQDs, resulting in an irregular size distribution. Consequently, the photovoltaic performance decreases because of the increase in Pe-CQD polydispersity. Here, we demonstrate the preparation of well-purified monodisperse CsPbI3-Pe-CQDs via size selection on the basis of gel permeation chromatography. Well-purified monodisperse Pe-CQDs exhibit improved photovoltaic performance and achieve a low Pe-CQD polydispersity. Furthermore, these Pe-CQDs show higher photoluminescence quantum yields, narrower full-widths at half-maximum, and lower Urbach energies, in comparison to irregular-sized Pe-CQDs without size selection. Therefore, CsPbI3-Pe-CQD solar cells comprising monodisperse Pe-CQDs show the highest power conversion efficiency (15.3%) and V OC (1.27 V) among the fully inorganic CsPbI3-Pe-CQD solar cells reported so far.

Quantum dots (QDs) are emerging photovoltaic materials that display exclusive characteristics that can be adjusted through modification of their size and surface chemistry. However, designing a QD‐based optoelectronic device requires specialized approaches compared with designing conventional bulk‐based solar cells. In this paper, design considerations for QD thin‐film solar cells are introduced from two different viewpoints: optics and electrics. The confined energy level of QDs contributes to the adjustment of their band alignment, enabling their absorption characteristics to be adapted to a specific device purpose. However, the materials selected for this energy adjustment can increase the light loss induced by interface reflection. Thus, management of the light path is important for optical QD solar cell design, whereas surface modification is a crucial issue for the electrical design of QD solar cells. QD thin‐film solar cell architectures are fabricated as a heterojunction today, and ligand exchange provides suitable doping states and enhanced carrier transfer for the junction. Lastly, the stability issues and methods on QD thin‐film solar cells are surveyed. Through these strategies, a QD solar cell study can provide valuable insights for future‐oriented solar cell technology.

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