Before you start planning how to spend that $20,000, here's the catch: the light must work in a refugee camp.
That means it has to be cheap, easy to maintain and hard to steal.
Most camps in Africa have no lighting system and darkness descends as the sun sets. This means women and girls have no safe place to relieve themselves for the next 12 hours.
"They are frightened to use the toilets at night," said Oxfam's Andy Bastable, one of the competition judges and an expert in water, sanitation and hygiene promotion (WASH) services.
"There have been many cases where women get abused on their way to, on their way back, or actually at the toilet."
In higher profile emergencies, like the influx of Syrian refugees to Jordan, toilets in camps are often provided with solar lighting. But donors and aid agencies rarely pay for long-standing camps in Africa to have the same facilities, making it more dangerous for women.
"They sometimes use a plastic bag or container inside their shelter or they wait and they go off in a group in the morning into the bush," said Bastable. "It's a very undignified practice."
Latrine lights are one of several technologies that the Humanitarian Innovation Fund (HIF) aims to develop by throwing the challenge out to the public, with the incentive of prize money.
HIF works to broker partnerships between humanitarian agencies, academics and the private sector to develop new ideas for use in emergencies.
The need for latrine lighting was identified by more than 900 beneficiaries, field practitioners and donors as one of the most pressing gaps in emergency WASH services.
"It's probably the biggest and the most thorough, proper, gap analysis that has ever been done," said Bastable.
Some of the gaps - like latrine lighting- will be addressed through open innovation, with grants given to the best ideas submitted. Others will be tackled through expert brainstorming sessions.
Bastable is hopeful that the process will focus people's energies on the need for improved sanitation - the top priority identified in the analysis.
"Nearly every week, I get contacted by a supplier or inventor of a new water filtration system. Everybody's very focused on the sexy bit of WASH, which is the water purification," he said.
"We have very little innovation around sanitation and still do it in emergencies as we did 20 years ago."
Contrary to popular perceptions, existing solar lighting products are not up to the task - despite Africa's sunny climate.
Solar panels and batteries to store the energy generated tend to be expensive and vulnerable to theft. In addition, the batteries usually last less than a year in countries like Kenya and South Sudan because the steep fluctuation between day and night temperatures wears them out.
Any innovations using solar power would have to improve on battery technology, as well as being small and theft-proof.
Bastable is open to all kinds of inventions.
"I want to be surprised by some of the good ideas," he said.
The deadline for submissions is March 16.