研究目的
Investigating the impact of photoactive layer thickness on the performance of organic solar cells, focusing on the accumulation of photo-generated charge carriers in intra-bandgap tail states and its effect on charge collection efficiency.
研究成果
The study concludes that the loss of photocurrent in thick organic solar cells is primarily due to charge accumulation in intra-bandgap tail states, which screens the internal electric field and prevents efficient charge collection. Purification of the donor polymer reduces tail state distribution and increases the maximum thickness for efficient operation, suggesting that minimizing tail state density is crucial for the development of efficient, thick organic solar cells.
研究不足
The study is limited to specific photoactive blends and may not generalize to all organic solar cell materials. The impact of tail states on device performance requires further investigation to fully understand the mechanisms involved.
1：Experimental Design and Method Selection:
The study employed transient optoelectronic techniques, air photoemission spectroscopy, Kelvin probe measurements, Mott-Schottky analyses, and device modelling to analyze the performance of organic solar cells with different photoactive blends.
2：Sample Selection and Data Sources:
Four different photoactive blends were used, including a small molecule donor BTR, and polymer donors PCDTBT and DT-PDPP2T-TT, with devices fabricated in typical organic bulk heterojunction architectures.
3：List of Experimental Equipment and Materials:
Equipment included a Keithley 2400 source meter, Newport 92193A-1000 solar simulator, Agilent 5500 atomic force microscope, and APS04 Air Photoemission system. Materials included PCDTBT, DT-PDPP2T-TT, BTR, and PC71BM.
4：Experimental Procedures and Operational Workflow:
Devices were fabricated on ITO glass substrates with varying photoactive layer thicknesses, followed by characterization of J-V response, AFM, SCLC, and impedance measurements.
5：Data Analysis Methods:
Data were analyzed using SCAPS software for device simulations, and charge carrier densities and lifetimes were determined from CE and TPV measurements.
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