Abstract
Interfacial materials are essential to the performance and stability of polymer solar cells (PSCs). Herein, solution-processed zirconium(IV) isopropoxide (Zr[OCH(CH3)2]4, ZrIPO) has been employed as an efficient cathode buffer layer between the Al cathode and photoactive layer. The ZrIPO buffer layer is prepared simply via spin-coating its isopropanol solution on the photoactive layer at room temperature without any post-treatment. When using ZrIPO/Al instead of the traditionally used Ca/Al cathode in PSCs, the short-circuit current density (Jsc) is significantly improved and the series resistance of the device is decreased. The power conversion efficiency (PCE) of the P3HT:PCBM-based device with ZrIPO buffer layer reaches 4.47% under the illumination of AM1.5G, 100 mW/cm2. A better performance with PCE of 8.07% is achieved when a low bandgap polymer PBDTBDD is selected as donor material. The results indicate that ZrIPO is a promising electron collection material as a substitute of the traditional low-work-function cathode for high performance PSCs.
Highlights
Polymer solar cells (PSCs) have been gaining increasing attention due to their promising prospects for low-cost, portable and flexible modules [1,2,3], and the solution processability makes them very easy to be fabricated via roll-to-roll techniques [4]
The certified power conversion efficiency (PCE) of single-junction PSCs has climbed above 11% since the bulk heterojunction (BHJ) architecture has been adopted to form a sandwich device [5,6], in which a nanoscale photoactive layer is sandwiched between the high work function anode and the low work-function (WF) cathode [7,8]
Alcohol-soluble ZrIPO with suitable energy level structure and ultrahigh transparency has been successfully applied as CBL in traditional BHJ-PSCs based on P3HT:PCBM and PBDTBDD:PCBM photoactive layer
Summary
Polymer solar cells (PSCs) have been gaining increasing attention due to their promising prospects for low-cost, portable and flexible modules [1,2,3], and the solution processability makes them very easy to be fabricated via roll-to-roll techniques [4]. The certified power conversion efficiency (PCE) of single-junction PSCs has climbed above 11% since the bulk heterojunction (BHJ) architecture has been adopted to form a sandwich device [5,6], in which a nanoscale photoactive layer is sandwiched between the high work function anode and the low work-function (WF) cathode [7,8]. Large scale practical application has been inhibited by the poor stability of the devices because the commonly adopted cathode buffer layer (CBL, e.g., calcium (Ca) or barium (Ba)) is prone to oxidative degradation as well as the instable photoactive layer and anode modification layer [9,10,11]. Considerable efforts have been directed to exploring a stable and solution-processable CBL between an active layer and a cathode since interfacial engineering is a critical factor for the stability improvement of PSCs [15].
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