Doped Spiro-OMeTAD May Not Be Essential for Efficient Indoor Perovskite Photovoltaics

Doped Spiro-OMeTAD May Not Be Essential for Efficient Indoor Perovskite Photovoltaics

by Simon Mansfield

Sydney, Australia (SPX) Aug 10, 2024

A new study challenges the conventional wisdom that doping Spiro-OMeTAD is essential for high-efficiency perovskite solar cells, particularly in indoor applications. Researchers explored the performance of lead halide perovskite (LHP)-based photovoltaic devices that utilize Spiro-OMeTAD as the hole-transport material, comparing doped variants with those left undoped.

Surprisingly, while the undoped Spiro-OMeTAD devices showed a modest efficiency of 7.7% under standard 1-Sun illumination, their performance dramatically improved under indoor lighting conditions.

At 1000 lux, these undoped devices reached an efficiency of 25.6%, which is quite close to the 29.7% achieved by their doped counterparts. This enhanced indoor performance is primarily due to a significant increase in fill factor at lower light intensities. The diminished effect of series resistance under such conditions plays a crucial role, allowing the undoped devices to operate more efficiently.

Moreover, the undoped devices demonstrated notable operational stability. When exposed to continuous white light, these devices saw about a 25% boost in maximum power point efficiency, indicating that they could potentially outperform doped Spiro-OMeTAD devices over extended use.

Additionally, the undoped variants exhibited lower hysteresis at very low-light levels and maintained an open-circuit voltage of approximately 0.65 V at 50 lux, suggesting enhanced reliability under these conditions.

These findings imply that while doping Spiro-OMeTAD remains crucial for maximizing the performance of LHP-based solar cells in outdoor or high-light scenarios, it may not be necessary for indoor applications.

The study also highlights that the efficiency of LHP-based solar cells under standard lighting does not necessarily predict their performance in low-light environments. This suggests a need to optimize photovoltaic structures specifically for the intended lighting conditions to achieve the best possible performance.

Research Report:Is Doping of Spiro-OMeTAD a Requirement for Efficient and Stable Perovskite Indoor Photovoltaics?