入射单色光-电子转化效率(Incident Monochromatic Photon-Electron Conversion Efficiency,IPCE)定义为流经闭合电路中的电子数与入射单色光的光电子数的比值,用来评价不同波长下的光电转化效率,是评价光电极光电化学性能的重要指标之一。
由于半导体材料对不同波长的入射光具有不同的响应,因此,测量光电极的IPCE对评估光电极对单色光光子的利用率会更加精确,进而在改进光电极提升其光电化学性能上更具针对性[1]。
IPCE计算公式如下[2]:
jph:光电流密度(mA·cm-2),通过计时电流法(恒电位)测得
h:普朗克常量(6.62×10-34 J·s)
c:光速(3.0×108 m·s-1)
e:单个电子所携带的电量(1.6×10-19 C)
Pmono:单色光的光功率密度(mW·cm-2)
λ:单色光波长
简化后可表示为公示(2)[1]:
jp:光电流密度(mA·cm-2)
jd:暗电流密度(mA·cm-2)
λ:入射单色光波长(nm)
pin:光电极受到的光功率密度(mW·cm-2)
光电极的光电流密度越大,IPCE值越高,可以通过改善光电极材料的电荷分离和收集效率,进一步提升光电极的光电流密度,从而提高IPCE数值。
泊菲莱科技PL-PES光谱光电系统可实现以入射光的波长为函数,在紫外、可见、近红外波长范围,自动表征测量半导体材料的光电流、光伏等光电性能参数,可与开尔文探针、电导探针等测试设备联用,可以控制输出光波长、光照射时间、与电化学工作站同步工作。PL-PES光谱光电系统主要应用于不同外加电压条件、不同光照波长、不同光强和不同电压及光照强度扫描下的光电流测试和特定光照波长下的开路电位测试等。
Fig.1 a)PL-PES光谱光电系统; b) IPCE曲线及光电流/电压行为谱
Fig. 2. a) IPCE at 0 V vs. Ag/AgCl[3]; b) IPCE at 1.2 V vs. Ag/AgCl[4]; c)IPCE [5]; d) IPCE at 1.2 VRHE; e) band gaps from photocurrent measurements[6];f) IPCEs at 0.6 and 1.2 VRHE, respectively[7]
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