Temperature and light dependent diode current in high-efficiency solution-processed small-molecule solar cells

• The positive temperature coefficient of the rectification ratio was shown.
• The dominating diode current mechanisms were determined in the dark.
• The illumination reduces the contribution of the Shockley–Read–Hall recombination.

This paper reports on the detail analysis of the DC electrical and photoelectrical properties of the high-efficient (η = 8.01% under standard 100 mW/cm2 AM1.5 illumination) small molecule bulk heterojunction (SM BHJ) solar cells p-DTS(FBTTh2)2/PC70BM. In this SM BHJ solar cell, the dark diode current is determined by the multistep tunnel-recombination via interface states at low forward bias (V < 0.65 V) and the interface state assisted thermionic emission at high forward bias (V > 0.65 V). The effect of illumination on the diode current was also quantitatively investigated. It was observed a reduced Shockley–Read–Hall recombination via interface states at large forward bias (from the maximum power point to the open-circuit conditions). The expression of the load I–V characteristic of the illuminated high-efficient SM BHJ solar cells was derived in the presence of the light dependent series and shunt resistance.

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