Effect of doping on the short-circuit current and open-circuit voltage of polymer solar cells

Abstract

The change in doping density in P3HT:PCBM based polymer solar cells (PSCs) with different processing solvents and with/without post-fabrication thermal treatment is investigated with capacitance-voltage measurement and optical microscopic imaging. The results suggest that both slow drying and thermal treatment facilitate the phase-separation and crystallinity of P3HT and PCBM, leading to low defect density and thus low p-type doping. Direct links between the doping density and the performance of the PSCs, specifically the short-circuit current (Jsc) and open-circuit voltage (Voc), are observed. The results show that doping density is one of the decisive factors affecting the photocurrent of the PSCs. Lower doping density leads to a wider depletion region, which is beneficial for carrier collection. The agreement between the calculation and the experiment suggests that the Voc increases monotonically with increasing doping densities in the PSCs. These rules consistently explain our results on the change of Jsc and Voc after thermal annealing in the PSCs with different processing solvents.

Numerical Investigation of Graphene as a Back Surface Field Layer on the Performance of Cadmium Telluride Solar Cell

“…When the doping concentration in the BSF layer increased from 10 15 to 10 17 cm −3 , the PV properties remained unchanged and, after that, started to decrease sharply with a further increase. Lower doping density leads to a wider depletion region, which is beneficial for the carrier collection and recombination process [ 53 ]. The optimum values of I sc = 2.09 A, V oc = 0.809 V, η = 15%, and FF = 88.55% were observed at 1 × 10 17 cm −3 of doping concentration, as shown in Figure 3 a,b.…”

Energy Tracing of Photovoltaic Cells

“…Here, we can have a more detailed discussion on the terms limiting the value of V oc . i) Under the open‐circuit situation, the generation ( G ) will balance with the recombination ( = G , where γ is the recombination rate, n the electron concentration, and p the hole concentration) [ 12,13 ] and the forward bias is equivalent to the splitting of Fermi level ; [ 28 ] therefore, the potential drop (i.e., = V bi − V ) in depletion region can be expressed bywhere n i is the intrinsic carrier density and N d ( N a ) the doping concentration of donor (acceptor). It can be seen that this potential drop is caused by the energy band bending, which is determined by the doping concentration, carrier recombination and generation rate.…”

“…It was discovered that the carrier recombination critically limits the V oc , so that the performances of the practical SCs are far from the theoretical expectation. [10][11][12][13][14] By constructing the advanced heterojunction interface (e.g., interface passivation and energy-band alignment), the interface recombination can be effectively diminished to obtain a favorable carrier transportation. [15,16] We also developed an optoelectronic model to quantitatively analyze the carrier loss channels, [17][18][19][20] and further identified the typical carrier thermodynamic losses by constructing an opto-electro-thermal (OET) model for better understanding the SCs.…”

The prospective application of a graphene/MoS2heterostructure in Si-HIT solar cells for higher efficiency

“…. 57 We can assume that V OC increased with N C /N V owing to an increase of Dp and Dn. As shown in Fig.…”

“…In a p-n junction, eV bi f 1 3 r , which affect the relative permittivity of the MoS 2 layer. 54,57 The generation of the e-h pair increases in the MoS 2 layer with an increase in the 3 r following Coulombs law as Ff 1 3 r , in which F is the electrostatic force between the electron and holes, but at the same time the increase in 3 r reduces eV bi . As a consequence of both of these effects, we obtained a constant V OC .…”