Mapping the Local Photoelectronic Properties of Polycrystalline Solar Cells Through High Resolution Laser-Beam-Induced Current Microscopy

Leite, Marina S.; Abashin, Maxim; Lezec, Henri J.; Gianfrancesco, Anthony G.; Talin, A. Alec; Zhitenev, Nikolai B.

doi:10.1109/jphotov.2013.2284860

Cited by 25 publications

(22 citation statements)

References 21 publications

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“…[ 18,[29][30][31][32][33][34][35] The local optoelectronic properties and changes in material composition have also been mapped using near-fi eld scanning optical microscopy (NSOM) probes as local sources of excitation. [36][37][38][39][40][41][42] Very recently, photoluminescence has emerged as a promising tool to map charge recombination [43][44][45] and carriers diffusion [ 46 ] with high spatial resolution. At low temperature (70 K), photoluminescence imaging with submicrometer resolution has been implemented to map a 10 meV quasi-Fermi level splitting in CIGS solar cells, where variations in the intensity signal were attributed to changes in the material composition.…”

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confidence: 99%

“…In particular, Kelvin probe force microscopy (KPFM) has been implemented to probe the electrical characteristics of a variety of PV materials and devices, ranging from organic materials and oxides to III–V semiconductors for multijunction designs and polycrystalline thin films . The local optoelectronic properties and changes in material composition have also been mapped using near‐field scanning optical microscopy (NSOM) probes as local sources of excitation . Very recently, photoluminescence has emerged as a promising tool to map charge recombination and carriers diffusion with high spatial resolution.…”

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confidence: 99%

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Nanoimaging of Open‐Circuit Voltage in Photovoltaic Devices

Tennyson

Garrett

Frantz

et al. 2015

Advanced Energy Materials

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voltage and the overall electrical behavior of a device strongly depend on the nonradiative recombination rate of the charge carriers within a material, which is affected by the defects inherently present within the semiconductor. Despite all the efforts in developing higher performance thin-fi lm polycrystalline solar cells, such as CdTe, CuIn x Ga (1− x ) Se 2 (CIGS), and Cu 2 ZnSnS 4 (CZTS), the difference between the theoretically predicted and the best experimentally achieved V oc is still considerably large (up to 0.6 V). [ 2,3 ] For Si, extensive research has been dedicated to design and implement nanostructured light-trapping architectures to boost light absorption; [4][5][6][7] however, there are very few experiments showing how the V oc is affected. For organic PV blends, the limited V oc observed in most bulk heterojunction solar cells is attributed to geminate and nongeminate losses; [ 8,9 ] nevertheless, local variations in V oc have never been measured. Thus, for any micrometer-and nanoscale structured PV device, assessing variations in V oc with nanoscale resolution and spatially resolving where recombination occurs within the material can potentially change the pathway for designing higher performance devices.Imaging methods based on atomic force microscopy (AFM) techniques have been extensively used to characterize the structural and electrical properties of PV materials and full devices. [10][11][12][13][14][15][16][17][18][19][20][21] In particular, Kelvin probe force microscopy (KPFM) has been implemented to probe the electrical characteristics of a variety of PV materials and devices, ranging from organic materials [ 9,[22][23][24] and oxides [ 25 ] to III-V semiconductors for multijunction designs [26][27][28] and polycrystalline thin fi lms. [ 18,[29][30][31][32][33][34][35] The local optoelectronic properties and changes in material composition have also been mapped using near-fi eld scanning optical microscopy (NSOM) probes as local sources of excitation. [36][37][38][39][40][41][42] Very recently, photoluminescence has emerged as a promising tool to map charge recombination [43][44][45] and carriers diffusion [ 46 ] with high spatial resolution. At low temperature (70 K), photoluminescence imaging with submicrometer resolution has been implemented to map a 10 meV quasi-Fermi level splitting in CIGS solar cells, where variations in the intensity signal were attributed to changes in the material composition. [ 47 ] Nevertheless, none of these imaging techniques provide a direct measurement of V oc within the material at operating conditions. A straightforward, universal, and accurate method to measure the V oc (and hence nonradiative recombination processes) with high spatial resolution in PV materials is still missing.Here, we present a new imaging technique based on illuminated KPFM to map the V oc of optoelectronic devices with nanoscale resolution <100 nm. We map the contact potential difference (CPD) of half or fully processed solar cells in the For most photovoltaic (PV) devices, the...

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Nanoimaging of Open‐Circuit Voltage in Photovoltaic Devices

Tennyson

Garrett

Frantz

et al. 2015

Advanced Energy Materials

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“…The imaging of local variations in photovoltage by KPFM is a non-destructive measurement technique that can be expanded to other PV materials, and only requires a bottom contact. To quantify and minimize the contribution of topography to the surface photovoltage measurements, the morphology of the surface of the samples can be modified by polishing, plasma etching, or Ga-ion beam milling processes [7]. Alternatively, depending on the morphology of the sample to be analyzed, heterodyne KPFM might be implemented instead, which allows for the analysis of very rough surfaces ..--.…”

Section: Resultsmentioning

confidence: 99%

“…Scanning probe microscopy techniques have been extensively used to characterize the electrical and optical properties of thin film solar cells [2]- [7]. In particular, photo assisted Kelvin Probe Force Microscopy (KPFM) [8] using a scanning tunneling microscope has been used to determine the band profile of the GBs, which was found to help the carrier separation [9].…”

Section: Introductionmentioning

confidence: 99%

Assessing local voltage in CIGS solar cells by nanoscale resolved Kelvin Probe Force Microscopy and sub-micron photoluminescence

Tennyson

Garrett

Gong

et al. 2014

2014 IEEE 40th Photovoltaic Specialist Conference (PVSC)

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Here we use nanoscale resolved Kelvin Probe Force Microscopy (KPFM) to locally probe the open circuit voltage in CIGS thin film solar cells. Illumination-dependent KPFM shows that the grain boundaries and grain cores present variations in surface photovoltage, as a consequence of the local variation of the open circuit voltage. Additionally, room temperature sub-micron photoluminescence (PL) scans were used to map the recombination centers in the polycrystalline CIGS films.Index Termssolar energy, thin-film, scanning probe microscopy, CIGS.

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“…Although NSOM is typically used for optical imaging, NSOM probes can also be used for SPCM measurements of photo-active samples. SPCM conducted with an NSOM probe, also known as near field scanning photocurrent microscopy and photoelectrochemical microscopy, has been successfully used to study nanoscale variation in photocurrent in photovoltaic materials, [42][43][44] and analysis of corrosion products. 45 NSOM-based SPCM offers similar opportunities for investigation of photoelectrodes at the nanoscale range.…”

Section: Scanning Photocurrent Methodsmentioning

confidence: 99%