Doped Spiro-OMeTAD may not be essential for efficient indoor perovskite photovoltaics
A new study challenges the conventional wisdom that doping Spiro-OMeTAD is essential for high-efficiency perovskite solar cells, especially in indoor applications. Researchers examined the performance of lead halide perovskite (LHP)-based photovoltaic devices using Spiro-OMeTAD as a hole transport material, comparing doped variants with variants that remained undoped.
Although the undoped Spiro-OMeTAD devices showed a modest efficiency of 7.7% under standard 1-Sun illumination, their performance surprisingly improved dramatically under indoor lighting conditions.
At 1000 lux, these undoped devices achieved an efficiency of 25.6%, which is quite close to the 29.7% achieved by their doped counterparts. This improved indoor performance is mainly due to a significant increase in fill factor at lower light intensities. The reduced effect of series resistance under such conditions plays a crucial role, allowing the undoped devices to operate more efficiently.
Moreover, the undoped devices showed remarkable operational stability. When exposed to continuous white light, these devices saw an approximately 25% increase in maximum power point efficiency, indicating that they could potentially outperform doped Spiro-OMeTAD devices during extended use.
Furthermore, the undoped variants showed lower hysteresis in very low light conditions and maintained an open-circuit voltage of approximately 0.65 V at 50 lux, indicating improved reliability under these conditions.
These findings imply that while Spiro-OMeTAD doping remains crucial for maximizing the performance of LHP-based solar cells in outdoor or high-light conditions, 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 indicates the 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 indoor perovskite photovoltaics?
