A research team in Japan has created the first universal model explaining how energy levels align inside perovskite solar cells — a breakthrough that could speed up development of cheaper, more efficient clean energy technology.
Perovskite solar cells have been one of renewable energy’s brightest success stories, posting record efficiency gains year after year. Now, scientists say they’ve solved a fundamental puzzle that has slowed progress: understanding exactly how electrical charges move through a critical internal layer of the device.
A team led by Hiroyuki Yoshida, a professor in the Graduate School of Engineering at Chiba University in Japan, has developed what researchers are calling the first universal model for energy level alignment at the interfaces inside perovskite solar cells. The findings, published March 14 in the Journal of Materials Chemistry A, could help engineers design better-performing solar cells faster and at lower cost — changes that matter for the broader push toward affordable clean energy.
Why Perovskites Matter
Perovskite solar cells have attracted enormous scientific and commercial interest because they convert sunlight to electricity at impressive rates, are lightweight, and can be manufactured through relatively inexpensive solution-based processes. That combination makes them suitable not just for rooftop panels but also for building windows, vehicle surfaces and portable electronics — applications where traditional silicon panels fall short.
A recent advance in the field has been the use of hole-collecting monolayers, or HCMs — ultrathin layers that gather positively charged particles, called holes, from the perovskite material and shuttle them toward an electrode. HCMs have helped push single-junction perovskite solar cells to 26.9% power conversion efficiency, a remarkable figure, while also improving how long devices last.
The Problem Researchers Were Trying to Solve
Despite rapid progress, scientists lacked a consistent theoretical framework for predicting how well a given HCM material would actually perform. Several competing models existed for describing the energy landscape at the interface between the electrode, the HCM and the perovskite, and researchers were applying them interchangeably — often without strong justification. The result was heavy reliance on costly trial and error when developing new materials.
Yoshida’s team tackled that problem by using advanced measurement techniques, including ultraviolet photoelectron spectroscopy and low-energy inverse photoelectron spectroscopy, to precisely map the energy properties of various HCM materials and perovskites. Those measurements fed into a new model that treats the electrode/HCM/perovskite interface as two distinct zones, each governed by well-defined physical principles.
What the Model Reveals
The model identified two factors as decisive for hole collection efficiency: a phenomenon called band bending, in which built-in electric fields gradually shift the energy landscape at a junction, and the interfacial energy barrier height, which describes how easily — or how difficultly — charges can cross from one material to another.
Source: Chiba University