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FTPS (CTS/ Trap State)

Fourier Transform Photocurrent Spectroscopy (FTPS)/ Highly Sensitive External Quantum Efficiency (HS-EQE)

The Most Sensitive Photocurrent and EQE/IPCE System in the World.

  In semiconductor devices, imperfect crystallinity often causes defect or trap states in the forbidden bandgap, which greatly affect the overall optical and electrical performance of the device. Because the absorption coefficient in the bandgap is extremely low, the generated photocurrent signal is extremely weak as well. Therefore, a highly- sensitive detection system is required.

  Enlitech’s FTPS is a highly sensitive photocurrent and external quantum efficiency (HS-EQE) spectroscopy system. It utilizes Fourier Transform Signal Processing technology to enhance and breakthrough the photocurrent signal detection limits. The lowest EQE level can be as low as 10-5% (7 orders)*. FTPS can be applied to detect the tail states of perovskite solar cells, charge transfer state of organic solar cells, which are the key to improve Voc loss mechanisms. Another common application is the Urbach Energy measuring.


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  • Direct spectroscopy evidence for trap states, defect states or charge transfer states.
  • Wavelength range: 1.1~2.07 eV (600nm~1100nm); option:0.7 eV~2 eV (600nm~1700nm).
  • Turn-key solution; generate reliable spectral data after installation. Time-saving and cost-effective (at least 1-year and 20k USD).
  • Complete training course including the operational and fundamental background training.
  • Proved by over 50 SCI journal papers.
  • Not just data acquisition, but also energy level fitting! Provide CTS and Urbach Energy level fitting software.
System Design
Fourier Transform Photocurrent Spectroscopy (FTPS)
10-5% (7 orders)* the detection dynamic of FTPS system can be 7 orders, but the lowest EQE level is determined by DUT's thermal noise itself.

Wavelength Range 1.1 eV ~ 2 eV
Min. Photocurrent Capability ≤ 100 fA
Dynamic Range ≥ 5 orders (>100 dB)
Repeatability >99 % (under AM1.5G)
Software Charge Transfer Energy Fitting, Urbach Energy Calculation


Voc loss mechanism and charge transfer state study on 16% efficiency organic photovoltaic cells.

  In 2019, Dr. JH Hou’s group from ICCAS adopted Enlitech’s PECT-600 and REPS systems to study the mechanism of increased open-circuit voltage in 16% efficiency organic solar cell with chlorinated acceptor system. The authors report a chlorinated non-fullerene acceptor, which exhibits an extended NIR optical absorption and contributes to short-circuit photocurrent (from EQE spectrum measured by Enlitech’s QE-R system).

  This system also reveals a higher Voc, which was explored by highly sensitive PV-EQE and EL-EQE techniques (FTPS PECT-600 and REPS systems). The main reason of increased open-circuit voltage is due to the significant reduction in non-radiative decay loss (0.206 eV). Therefore, this chlorinated acceptor can simultaneously increase the short-circuit current density and the open-circuit voltage. The excellent result is published in Nature Communications.


Over 16% efficiency organic photovoltaic cells enabled by a chlorinated acceptor with increased open-circuit voltages.

Yong Cui, Huifeng Yao, Jianqi Zhang, Tao Zhang, Yuming Wang, Ling Hong, Kaihu Xian, Bowei Xu, Shaoqing Zhang, Jing Peng, Zhixiang Wei, Feng Gao & Jianhui Hou

Nature Communications volume 10, 2515 (2019)


  Organic PV INFO reported on 18. February 2021 that it is crucial to understand and minimize performance losses for achieving the higher OPV efficiencies. The FTPS system of PECT-600 is helping researchers understand the details about the Voc loss mechanisms.  Link

Ultra-sensitive EQE external quantum efficiency FTPS reported by OrganicPV info

~18% Organic Solar Cell

Enli Tech’s Voc loss Analysis tool was used for developing new material of organic photovoltaics cells, which achieved nearly 18% efficiency.  

~17% Organic Solar Cell

Enli Tech’s quantum efficiency measurement system was adopted to Voc loss calculation and organic solar cells with nearly 17% efficiency developed.

Perovskite Solar Cell (Voc=1.16V)

Enli Tech’s Voc loss analysis technique provides the provement of suppressing non-radiative recombination loss with Lewis base. The Voc of perovskite solar cells was improved from 1.10 V to 1.16 V.

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